THE MACKINAC CHANNEL

The now-submerged Mackinac Channel is an incised river channel that lies below the Straits area. It was first described by U of M Professor George Stanley in 1938. He used US Army Corps of Engineers Lake Survey sounding sheets and some early bathymetric contours to locate the channel.  Stanley was among the first to recognize that significant lowering of water levels in both Lake Michigan and Lake Huron occurred about 10,000 years ago. At that time, both lakes drained to the sea through an isostatically-depressed valley in the North Bay (Ontario) area. This lowstand in Lake Michigan (Lake Chippewa) was at a slightly higher water level than that in Lake Huron (Lake Stanley), with drainage of Lake Michigan occurring through the Mackinac Channel. The map below shows the channel as it was known from bathymetry several years ago.
    The name given to the lowstand in Lake Huron honors Professor Stanley.  Hough (1955) referred to this channel in the Straits of Mackinac as the Mackinac River, but in keeping with accepted principles of applying terminology to water-covered topographic features, we refer to it as the Mackinac Channel.  Note that the channel even meanders, like modern rivers, around Mackinac Island.
    New bathymetry data has enabled scientists to construct a more accurate map of the Mackinac Channel (shown below).  The map provides an integrated view of the Mackinac Channel and the adjoining lakefloor topography.  Channel depths of about 35m occur NW of Waugoshance Point, and at a point north of Garden Island, where the main channel crosses resistant bedrock.

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This material has been compiled for educational use only, and may not be reproduced without permission.  One copy may be printed for personal use.  Please contact Randall Schaetzl (soils@msu.edu) for more information or permissions.